Re: [PATCH v2 RFC] userns: Convert xfs to use kuid/kgid where appropriate

Dwight Engen
2013-06-28T16:16:27Z

On Fri, 28 Jun 2013 10:25:52 -0500
Serge Hallyn <serge.hallyn@ubuntu.com> wrote:

> Quoting Dave Chinner (david@fromorbit.com):
> > On Thu, Jun 27, 2013 at 08:02:05AM -0500, Serge Hallyn wrote:
> > > Quoting Dave Chinner (david@fromorbit.com):
> > > > On Wed, Jun 26, 2013 at 05:30:17PM -0400, Dwight Engen wrote:
> > > > > On Wed, 26 Jun 2013 12:09:24 +1000
> > > > > Dave Chinner <david@fromorbit.com> wrote:
> > > > > > > We do need to decide on the di_uid that comes back from
> > > > > > > bulkstat. Right now it is returning on disk (==
> > > > > > > init_user_ns) uids. It looks to me like xfsrestore is
> > > > > > > using the normal vfs routines (chown,
> > >
> > > I might not be helpful here, (as despite having used xfs for years
> > > I've not used these features) but feel like I should try based on
> > > what I see in the manpages. Here is my understanding:
> > >
> > > Assume you're a task in a child userns, where you have host uids
> > > 100000-110000 mapped to container uids 0-10000,
> > >
> > > 1. bulkstat is an xfs_ioctl command, right? It should return the
> > > mapped uids (0-10000).
> > >
> > > 2. xfsdump should store the uids as seen in the caller's
> > > namespace. If xfsdump is done from the container, the dump
> > > should show uids 0-10000.
> >
> > So when run from within a namespace, it should filter and return
> > only inodes that match the uids/gids mapped into the namespace?
>
> I would think they should all be returned, with uid/gid being -1.

I agree, so I think bulkstat should return the uids with
from_kuid_munged(current_user_ns(), VFS_I(ip)), so it returns the
same values that stat(2) would. This would mean callers in
init_user_ns see the same values they do today. Callers inside
a userns will see mapped values, but note that they have to be
CAP_SYS_ADMIN in init_user_ns, which I wouldn't expect to normally be
the case.